1. Field of the Invention
This invention relates to disk drives. In particular, this invention relates to a method of making a head disk assembly of a hard disk drive by using a fixture for a head-disk merge operation.
2. Description of the Related Art and Related Information
A huge market exists for hard disk drives for mass-market host computer systems such as servers, desktop computers, and laptop computers. To be competitive in this market, a hard disk drive must be relatively inexpensive, and must accordingly embody a design that is adapted for low-cost mass production. In addition, it must provide substantial capacity, rapid access to data, and reliable performance. Numerous manufacturers compete in this huge market and collectively conduct substantial research and development, at great annual cost, to design and develop innovative hard disk drives to meet increasingly demanding customer requirements.
Each of numerous contemporary mass-market hard disk drive models provides relatively large capacity, often in excess of 1 gigabyte per drive. Nevertheless, there exists substantial competitive pressure to develop mass-market hard disk drives that have even higher capacities and that provide rapid access. Another requirement to be competitive in this market is that the hard disk drive must conform to a selected standard exterior size and shape often referred to as a "form factor." Generally, capacity is desirably increased without increasing the form factor or the form factor is reduced without decreasing capacity.
Satisfying these competing constraints of low-cost, small size, high capacity, and rapid access requires innovation in each of numerous components and methods of assembly including methods of assembly of various components into certain subassemblies. Typically, the main assemblies of a hard disk drive are a head disk assembly and a printed circuit board assembly.
The head disk assembly includes an enclosure including a base and a cover, at least one disk having at least one recording surface, a spindle motor for causing each disk to rotate, and an actuator arrangement. The printed circuit board assembly includes circuitry for processing signals and controlling operations.
Actuator arrangements can be characterized as either linear or rotary; substantially every contemporary cost-competitive small form factor drive employs a rotary actuator arrangement.
The rotary actuator arrangement is a collection of elements of the head disk assembly; the collection typically includes certain prefabricated subassemblies and certain components that are incorporated into the head disk assembly. The prefabricated assemblies include a pivot bearing cartridge and, in some cases, a prefabricated head stack assembly which may include the pivot bearing cartridge. Other components of the rotary actuator arrangement are permanent magnets and an arrangement for supporting the magnets to produce a magnetic field for a voice coil motor. The prefabricated head stack assembly includes a coil forming another part of the voice coil motor. The prefabricated head stack assembly also includes an actuator body having a bore through it, and a plurality of arms projecting parallel to each other and perpendicular to the axis of the bore. The prefabricated head stack assembly also includes head gimbal assemblies that are supported by the arms. Each head gimbal assembly includes a load beam and a head supported by the load beam.
In the course of making a head disk assembly, the heads are merged with the disks during an operation known as a "head-disk merge operation." With reference to Related Art FIG. 1, a head disk assembly 100 is shown which includes a base 102, a spindle motor 104, and a plurality of disks 106 mounted on the spindle motor. A corresponding set of heads 108 is positioned proximate to an outside diameter of the disks. A merge comb (not shown) separates the heads as shown in FIG. 1 until a sufficient clearance is detected between each head and each corresponding disk. When sufficient clearance is detected, the heads are then merged with the disks and the merge comb is removed.
In order to detect the clearance, a prism 110 is positioned proximate the heads such that a reflecting mirror surface 107 is positioned over a side wall 105 of base 102. Side wall 105 is relatively short since the head disk assembly includes a stack of relatively few disks (three are shown) which allows a relatively large prism 110 to be lowered partly into an interior of base 102 such that mirror surface 107 is positioned over side wall 105. Such a relatively large prism and its position relative to base 102 allowed the clearances to be detected simultaneously. A light beam 112 originating from a light source beyond another side wall 114 and propagated towards side wall 105 was used to detect the clearance.
In order to increase capacity of a hard disk drive, the number of disks is typically increased. When the number of disks increases, the height of the side walls correspondingly increases which prevents the use of relatively large prism 110 to detect clearance. In other words, the thickness of the prism prevents the positioning of mirror surface 107 proximate to the bottom disk and corresponding heads. Holes may be created in such a base to detect clearance by visual inspection or via a suitable lens/camera system. However, such holes need to be sealed after a head-disk merge operation is completed which increases the costs of making a head disk assembly and which may introduce contaminants into its interior.